IBDP CORE>TOPIC 2>2.1 CELL THEORY

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ASSESSMENT STATEMENT

2.1- CELL THEORY2.1.1 Outline the cell theory. 2.1.2 Discuss the evidence for the cell theory. 2.1.3 State that unicellular organisms carry out all the functions of life. 2.1.4 Compare the relative sizes of molecules, cell membrane thickness, viruses,bacteria, organelles and cells, using the appropriate SI unit.2.1.5 Calculate the linear magnification of drawings and the actual size of specimens in images of known magnification.2.1.6 Explain the importance of the surface area to volume ratio as a factor limiting cell size.2.1.7 State that multicellular organisms show emergent properties. 2.1.8 Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others.2.1.9 State that stem cells retain the capacity to divide and have the ability to differentiate along different pathways.2.1.10 Outline one therapeutic use of stem cells.

students will watch the cell theory video and there will be class discussion that will lead to the outline ad evidences of cell theory. (2.1.1 and 2.1.2)

watch video on amoeba biology and class discussion leading to stating that unicellular organisms carry out all functions of life. (2.1.3)

2.1.1 Outline the cell theory. 2.1.2 Discuss the evidence for the cell theory.

What was the importance of microscopes?

What was the contribution of Robert Hooke?

Which are the other scientists and what is their contribution?

What conclusion can be derived from the video?

Three principles of cell theory 1.All living things are composed of one or more cells.2.Cells are the smallest units of life.3.Cells come only from existing cells.

Two concepts that can be added today-

Cells contain blueprint for their growth, development and behaviour.

Cells are site of all metabolic activities.

2.1.3 State that unicellular organisms carry out all the functions of life.

What type of an organism is amoeba?

What according to you are major functions of a living cell?

What functions are being carried out by the amoeba?

Does amoeba manage to perform all the activities a human can perform?

What can you conclude from this?

All organisms – unicellular or multicellular carry out all the functions of life-

CHECK THIS SITE------SIZES OF CELLSAll organisms are made up cells that are tiny….visible only through a microscopeThey have different shapes and are of different sizes.Why do cells need to be small?What is the significance of cells taking different shapes?

2.1.6 Explain the importance of the surface area to volume ratio as a factor limiting cell size. (ACTIVITY- LAB)

We perform an activity as shown in the video beside to find the importance of surface area to volume ratio for a cell.

You are given agar blocks with food colour.

Cut the blocks into three different sizes.(2 sets)

Keep them in the given solution.(sodium hypochlorite- bleaching agent)

Surface area to volume ratio as a factor limiting cell size

1.As size increases both surface area and volume increase,2.However volume increases more / ratio of surface area to volume decreases as size of cell increases;3.Rate of metabolism is a function of its mass to volume ratio;4.Surface area limits/affects the rate at which substances can enter (or leave) the cell;5.Volume determines the rate at which material is produced/used;6.Oxygen/nutrients/substances will take too long to diffuse into/out of the centre of the cell if it is too big;7.Excretory products would take too long to be eliminated;8.Heat will take too long to be eliminated;9.Example of cell adaptation to increase the ratio of surface area: volume e.g. root hair cell;

LAB-2 CALCULATING THE LINEAR MAGNIFICATION

Stencil to be solved in class- The answers for these will be uploaded.

2.1.7 State that multicellular organisms show emergent properties.

Organisms can achieve more than the sum of what each part could achieve individually.

Cells perform their task when they interact with each other rather than when they are alone.

2.1.8 Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others.

Students watch the video and class discussion leading to cell differentiation

Differentiation is development in specific waysCells carry out specialized functionsConsidering a differentiated cell in a multicellular organism-Cells have all genes so could develop in any way. Some genes are expressed but not others.The position / hormones / cell to cell signals / chemicals determine how a cell develops; A group of differentiated cells is a tissue

2.1.9 State that stem cells retain the capacity to divide and have the ability to differentiate along different pathways. (ACTIVITY- DEBATE)

students watch the videos…..class discussion leading to what are stem cells?, where do we get stem stems from and what is its importance?then have a debate in the class- "Embryonic stem cells- boon or bane."

RULES AND RUBRICS FOR THE DEBATE

Answer the following questions-1. what are stem cells?2. Mention the types of stem cells.3. Why are embryonic stem cells preferred?4. What are the limitations of using embryonic stem cells?5. List some of the incurable diseases that can be cured with stem cells.

2.1.10 Outline one therapeutic use of stem cells.

Stem cells are cells that retain the capacity to divide and have the ability to differentiate along different paths into all types of cells

These cells are pluripotent/totipotent;

Stem cells are derived from blastocysts/human embryos, left over from IVF/placenta/umbilical cord/some adult tissues;

New techniques/technologies rely on replacing diseased/dysfunctional cells with healthy/functioning ones;

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